1. Field of the Invention
This invention relates, in general, to power line communication systems and, more specifically, to conductor arrangements for transferring communication signals between primary and secondary power distribution lines.
2. Description of the Prior Art
Automated power distribution systems which perform various functions, such as remote meter reading and selective load reducing, require the use of a distribution power line communication system. The distribution portion of the communication system conveys information between a substation and the electrical load at the customer location. This information must be transferred along the subtransmission or primary distribution line, the secondary distribution lines, and the service lines which extend to the customer locations.
Many different types of distribution power line communication systems have been described in the literature and have been used to some extent for actual communication purposes. One type of communication system transfers signals along the primary portion of the distribution system by using one of the high-voltage conductors and the common neutral return or ground conductor. Other types of communication systems use two of the high-voltage conductors. With either method, difficulty is encountered due to power factor correcting capacitors connected to the primary distribution line which severely attenuate the communication signals. Other types of communication systems have been used, but the problems of considerable signal attenuation and multipath propagation have not been satisfactorily solved.
The use of existing conductors located along the power distribution system is advantageous from the standpoint of providing an economical communication system. Consequently, it is advantageous to use a minimum amount of additional equipment or facilities to provide the carrier communication system. In addition, expensive components, such as couplers between the primary and secondary distribution lines, must be used sparingly to provide an economical communication system. Therefore, it is desirable, and it is an object of this invention, to provide an economical distribution power line communication system which provides high quality information transmission with a minimum of additional cost to the power distribution system.